ECM Power Source Circuit [10/2013 - ]: Description
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When the power switch is turned on (IG), auxiliary battery voltage is applied to IGSW of the ECM. The output signal from the MREL terminal of the ECM causes a current to flow to the coil, closing the contacts of the integration relay (EFI MAIN relay) and supplying power to terminals +B and +B2 of the ECM.